BROMINK 



2 5 



of volume change. As has been said, that part of the curve below 46 

 atmospheres is extrapolated, but an error occurring in it could have no 

 effect on the curve above, for this depends entirely upon the actual 

 observations. Since the calculation is somewhat complicated, it may 

 be well to state that it was performed from beginning to end by each 

 of the authors independently on different kinds of coordinate paper, 

 with precisely similar results. The plot being 40 centimeters high 

 and 33 centimeters wide, a considerable degree of accuracy was ob- 

 tained. It was easy to distinguish 0.02 centimeter or 1/2000 of the 

 maximum values. 



Thus the quantity given in the last column of the preceding table, 

 plotted in the direction of ordinates on the curve marked bromine in 

 the chart is 



[w - w> + 0.000 o Ql 6w" (P.-P^^^-^ + a n = (ft - ft>)P v 



From the curve it is at once clear that the compressibility decreases 

 rapidly as the pressure increases. In the table below, the values of 

 ft ft' are given for each hundred kilograms per square centimeter ex- 

 pressed in fractions of the original volume. The value between o and 

 100, being partly extrapolated, is enclosed in brackets. These values 

 were taken directly from the curve. 



Compressibility of Bromine at 20 C. 



Thus the compressibility of bromine is about sixteen times as great 

 as that of mercury at low pressures. The difference of temperature 

 (3 ) accounts in part for the difference between these results and the 

 preliminary ones given on page 10. 



Iodine. 



In order to prepare suitable material, "chemically pure" iodine 

 was mixed with pure potassium iodide, the two being finely ground, 

 and the iodine was sublimed, twice in succession. 



LIBRARY 



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